This invention relates in general to silk-screen printing machines and, more particularly to a printing table therefor having adjustably positionable work-engageable reference pins.
As is well known, many articles of work, such as rigid plates which, for example, include supports for printed circuits, must be properly positioned and fixed to the printing tables of silk-screen printing machines for maintenance against undesired shifting during the printing process. A widely utilized expedient for such purpose comprehends the provision of holes through the bottom of the work for accepting pins or dowels projecting upwardly from the printing table. Heretofore, the customary embodiment of such expedient has been the provision of a groove in the front side of the printing table for receiving a plurality of blocks slideable therein with each carrying a pin. By using suitable clamping means, such blocks can be maintained in a selected position which is dictated by the arrangement of the reference holes provided in the work. It will be seen that since the blocks are incapable of disposition except in a fixed linear path, the location of the reference holes in the work is dictated by the limited adjustability range of the blocks. Thus, such system of positioning is undesirably restricted. Furthermore, as it is preferable to effect the printing operation in a direction longitudinally of the work, with any slight play between the reference holes and coordinating pins, there will be certain oscillations or shifting of the work, particularly when the work constitutes relatively long plates whereby such oscillations prevent the high degree of accuracy required. Accordingly heretofore in order to avoid such obvious drawbacks, lengthy work plates were printed in a transverse or crosswise manner with attendant difficulties and resultant printing imperfections, all being well known to those skilled in the art.
Therefore, it is an object of the present invention to provide a table adapted for adjustable positioning of work-engaging reference pins in a multitude of directions within the plane of the printing table whereby the related holes in the work may be located at the most suitable points thereon.
It is another object of the present invention to provide a printing table of the character stated which incorporates rotatable elements on the table having a radially extending groove within which a reference pin-carrying block is slideably disposed so that the latter may be located within an infinitude of positions.
It is another object of the present invention to provide a printing table of the character stated which also embodies grooves for slideably disposed reference pin-carrying blocks so that the pins of the latter may cooperate with the pins carried upon the discs to effect reliable engagement with the work at mutually spaced points for maintaining the work in a rigid state during the printing operation.
It is a still further object of the present invention to provide a printing table of the type stated which may be most economically manufactured; which may be easily operated; which is markedly versatile for accommodating a multiplicity of hole arrangements in the work; the use of which assures of requisite disposition of the work for high fidelity in the printing procedure; and which is extremely durable in usage.